Although many other factors may contribute to the excess morbidity and mortality from asthma which is seen in the inner city, strong epidemiologic evidence now points to cockroach allergen exposure as an important risk factor. Not only is cockroach infestation predominantly a problem of the inner city, but it is one that potentially can be changed. We have been able to reduce indoor cockroach allergen levels in pilot studies and now propose to conduct an intervention trial to test the hypothesis that reducing home environmental cockroach will improve chronic asthma control in children. We will recruit 100 children aged 6-12 years with moderately severe asthma who have a positive skin test to cockroach, who are living in a home which is infested with cockroaches and which has Bla g I concentration of greater than 2 U/gm, who do not have a furred pet and whose families own a working vacuum cleaner. During an baseline period of 4 months, children will be evaluated and maintain a diary of symptoms, peak expiratory flow rate (PEFR) and medication use. They will visit once a month to evaluate their diary, to confirm medication use by weighing beta adrenergic inhalers to measure PEER and to receive education regarding asthma self management and allergen avoidance. We will visit their home to inspect and collect settled dust for cockroach (Bla g I and II) allergen analysis. After completing the baseline period, we will randomize 50 children to roach intervention, and 50 to control intervention for a 6 month double blind trial. Roach intervention will consist of extermination from a professional pest control company combined with mattress covers and monthly cleaning by professional home cleaners. Control intervention will consist of monthly cleaning and mattress covers. Cleaning technicians will also monitor live roach population with passive traps and inspection as well as collect settled dust for allergen analysis. Families will maintain diaries and we will continue to evaluate them at clinic visits every 2 months during the 6 month period. Children will perform a methacholine inhalation challenge before and after intervention. The effect of environmental intervention in the 2 groups will be compared in terms of the primary clinical variable, beta adrenergic medication use, and the primary process variable, settled dust cockroach allergen concentrations. Secondary variables, including symptom scores, PEFR, acute care visits, school loss, cockroach numbers and methacholine responsiveness will also be compared.